Hoist drum control

ABSTRACT

A hoist cable drum control having a spring set, normally engaged drum brake and a variable torque converter for driving the drum, in which a control device initiates cable take-up and slips the brake, and drum rotation is sensed to thereafter disengage the brake. Control forces on the converter and the brake are proportional so that as torque is reduced the brake comes on smoothly. Cable is payed off the drum through a reverse driving hydraulic motor actuated simultaneously with release of the brake and capable of being overridden by the torque converter to control &#39;&#39;&#39;&#39;lowering&#39;&#39;&#39;&#39; movement. A clutch engaged by initial operation of the control device permits multiple drums to be driven by the converter.

United States Patent Sieracki 1 June 25, 1974 [73] Assignee: The Manitowoc Company, Inc.,

Manitowoc, Wis.

22 Filed: July 25,1973

[21] App]. No; 382,544

[52] U.S. C1 254/173 R [51] Int, Cl. 866d 1/50 [58] Field of Search 254/172, 173 R [56] References Cited UNITED STATES PATENTS 2,945,675 7/1960 Fischer 254/173 X 3,125,819 3/1964 Kaufmann 254/173 X 3,158,355 11/1964 Wilson 254/173 3,477,695 11/1969 Noly 254/173 X Primary Examiner-Robert B. Reeves Assistant Examiner-Thomas E. Kocovsky Attorney, Agent, or FirmWo1fe, Hubbard, Leydig, Voit & Osann, Ltd.

[5 7] ABSTRACT A hoist cable drum control having a spring set, normally engaged drum brake and a variable torque converter for driving the drum, in which a control device initiates cable take-up and slips the brake, and drum rotation is sensed to thereafter disengage the brake. Control forces on the converter and the brake are proportional so that as torque is reduced the brake comes on smoothly. Cable is payed off thedrum through a reverse driving hydraulic motor actuated simultaneously with release of the brake and capable of being overridden by the torque converter to control lowering movement. A clutch engaged by initial operation of the control device permits multiple drums to be driven by the converter.

3 Claims, 3 Drawing Figures PATENTEDJUNZSIBH SHEET 1 BF 2 MQW I'IOIST DRUM CONTROL This invention relates generally to hoist drums for cable actuated lifting machinery and more particularly concernsa control system for such hoist drums.

Lifting machinery such as cranes utilize cable, often rigged as multi-part line, for positioning booms and lifting a load relative to a boom with the cable being payed out or taken in on powered hoist drums. Conventionally, such hoist drums are selectivelyclutched to a source of power which, preferably, can be controlled to deliver variable torque for speed and load flexibility. Also, drum brakes are normally provided to lock the drums so as to hold the cable when under high tensions loads.

Considerable skill is required of an operator to control clutches, brakes and power sources to obtain smooth movement of a load through a hoist drum particularly when the loads are very high as is typical of modern cranes. Tight safety regulations being considered or adopted by various crane users or authorities do not leave it to operator skill and require automatic braking so that the cable cannot be unintentionally run from a drum. While automatic braking sounds like a simple addition for a control system, the problem is greatly complicated by the need for smooth transition between the hoist drum being driven under power and being locked in position by a brake. Such a smooth transition is essential if shock loading of the cable is to be avoided.

Accordingly, it is the primary aim of the invention to provide a hoist drum control which automatically brakes the drum and yet provides smooth transition, without shock loading, between braking and driving the drum.

It is also an object of the invention to provide a control of the above character which affords smooth, noshoek operation whether the cable is being driven onto or off of the drum.

Another object is to provide a hoist drum control as described above which gives one lever control of a drum from braking to full power under all load conditrons.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIG. I is a schematic of a control system embodying the present invention;

FIG. 2 is a diagram showing alternate positions of one of the control levers otherwise appearing in FIG. 1; and

FIG. 3 is a fragmentary section of a portion of the brake structure embodied in the control system of FIG. I.

While the invention will be described in connection with a preferred embodiment, it will be understood that I do not intend to limit the invention to that embodiment. On the contrary, I intend to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Turning to FIG. 1, there is schematically shown a pair of cable hoist drums l and 11 suitable for use in a crane adapted to be driven, from an engine 12 supplying a source of torque, under the control of a system embodying the invention. The drums I0, 11 are held 2 I normally locked by band brakes l3 and 14, respectively, including (see FIG. 3) brake shoes 21 engaging a cylindrical portion of each drum and mounted on a band 22 anchored at one end by a link 23 and operated at the other end by an assembly including a bell crank 24. counterclockwise rotation of the bell crank 24 rotates a lever 25 clockwise through a link 26, which pulls a link 27 connected to the free end of the band 22 so as to back that end of the band from the circumscribed drum surface thereby releasing the brake. The brake is normally spring set by a heavy spring 28, urging the bell crank 24 clockwise, positioned in an actuator 30, in this case pneumatic, which opposes the force of the spring 28 when supplied with air under pressure. With the force of the spring 28 removed, a take-up spring 29 swings the bell crank 24 counterclockwise so as to release the brake.

Because of the wrap-around nature of the brake band 22, the brake 13 is self-energizing against rotation of the drum 10 in a clockwise direction, as seen in FIG. 3, which is the direction of drum rotation that pays cable out. Rotation of the drum in the opposite, cable take-up, counterclockwise direction will tend to unwrap the brake band 22 so that, even with the brake on, the drum can be driven to take in cable and the brake will slip. The brakes l3, 14 are alike in function and actuation.

The drums 10, 11 are driven through a converter 35 interposed between the engine 12 and thedrums. The converter, preferably of the type shown in more detail in US. Pat. Nos. 3,221,896 and 3,335,568, issued Dec. 7, 1965 and Aug. 15, 1967, respectively, includes a control member sleeve 36 interposed between a driving impeller 37 and a torque output turbine 38. The impeller 37 is mechanically connected to the engine 12 and the turbine 38 is mechanically connected to the drums 10, 11. With the sleeve 36 in a first blocking position, fully to the right as schematically indicated in FIG. I, no torque is transmitted from the impeller 37 to the turbine 38. The sleeve 36 can be shifted from the first position through an infinitely variable range of positions in which smoothly increasing amounts of torque are transmitted from the engine 12 to the drums.

For moving the sleeve 36, a spring 41 normally holds the sleeve in its first block position and a pneumatic actuator 42 opposes the spring and, when supplied with air under pressure, positions the sleeve. By modulating the air flow to the actuator 42, the sleeve can be variably positioned and the torque transmitted by the converter 35 precisely adjusted.

In operation, the engine 12 is normally operated at a constant speed in a direction to drive the drums, when torque is applied through the converter 35, in the direction to take up cable and thus lift whatever load is attached to the cable.

In accordance with the invention, each of the drums 10, 11 .is associated with a respective control device in the form of a manually positionable lever 43 or 44 each operating a throttling valve 45 for applying proportional forces through the actuators 30 and 42, and each drum is coupled to a respective rotation sensor 46 that, when slight rotation of the drum in the cable take-up direction is detected, completes an. electrical circuit to an associated solenoid valve 47 which is normally closed blocking air flow to, and thus force application by, the associated actuator 30. As a result of this arrangement, the operator of the control system can move one of the levers 43, 44 to gradually open the associated valve 45 and apply a gradually increasing force through the actuator 42 to slide the sleeve 36 and thus impose increasing torque from the engine 12 onto the associated drum. When the torque exceeds the torque load of the cable, the drum will begin to rotate in the cable take-up direction, slipping the associated brake 13 or 14. When the threshold of the associated rotation sensor 46 is exceeded, preferably when the drum rotates at about 0.] rpm, the sensor engergizes and opens the associated valve 47 to apply force through the actuator 30 that releases the associated brake 13 or 14. The speed of the lift is thereafter dependent upon the position of the lever 43 or 44 and thus the position of the sleeve 36.

To stop the cable take-up sequence, the lever 43 or 44 being operated is moved to gradually close the associated valve 45, reducing the force through the actuator 42 and thus moving the sleeve 36 to smoothly reduce the torque on the drum. This downward modulation of air pressure also affects the associated brake actuator 30 so that, as the torque is reduced, the associated brake 13 or 14 is gradually allowed to come on under the urging of a spring 28. In this way, the drum comes to a smooth, fully braked stop with no shock load-producing jerkiness.

So that a single converter 35 can selectively power the two drums l and 11, clutches 51 are interposed between the converter 35 and the drums 10, 11 with the clutches being under the control of actuators 52. Open-shut valves 53 deliver air under pressure to the associated actuators 52, and the valves 53 are connected respectively to the control levers 43, 44 so that initial movement of either one of the control levers opens the associated valve 53 to engage the associated clutch 51 before the valves 45 are opened to control the actuators and 42. In the preferred embodiment, the first approximate ten degrees of movement of a control lever to the position shown as 43a in FIG. 2 from the vertical OFF or rest position places the lever in a detented, clutch engaged, position wherein the associated valve 53 is open and the valve 45 is not yet initially opened. Thus, in the lever 43a position, the converter is clutched to the drum associated with the lever 43 and thereafter movement of the lever into a 43b range operates the system as otherwise described.

To pay out cable and thus lower a load, a hydraulic motor 55 is coupled to the clutches 51 on the output side of the converter 35 and is operated to drive the drums 10, 11 in a direction to pay out cable. Fluid under pressure is supplied to the motor 55 through a normally closed valve 56 opened by a pneumatic actuator 57 controlled by a solenoid operated valve 58 which is energized by depressing one of a pair of pushbuttons 59 on the respective control levers 43, 44. Depressing either one of the pushbuttons 59 also releases the associated brakes 13, 14 by energizing a solenoid 61 controlling a normally closed valve 62 so as to apply air pressure to the associated actuator 30.

As can now be understood, movement of one of the control levers 43, 44 to the detented, lever 43a position engages the associated clutch 51 and then, by operating the pushbutton 59, the drum brake 13 or 14 is released and the hydraulic motor drives the clutched drum in the cable payout direction. If, because of a heavy load, the cable is pulling off of the drum too rapidly, further movement of the control lever 43 or 44 brings the converter 35 into play applying torque opposing rotation of the drum so that cable payout can be selectively slowed, stopped or even reversed. As those familiar with the art will appreciate, power available through the converter 35 is significantly greater than that developed by the small motor 55 whose function is to, in effect, simply push cable from the drum. 1f the motor 55 is slowed 0r stalled, the driving hydraulic fluid is dumped through a pressure relief valve 63.

To stop paying out cable, the system operator, in what is virtually one movement, pushes the control lever 43 or 44 through the clutch engaged position to the rest position and releases the pushbutton 59. This stops the motor 55, applies the brake 13 or 14, opens the clutch 51 and interrupts torque flow through the converter 35 if the latter had been in use.

In the illustrated arrangement, brake bypass valves 65 are associated with each of the actuators 30 so as to permit operation of a selected one of the actuators and overcome the force of the brake setting spring 28. Brake control can then be had by a conventional foot pedal connected to the bell crank 24 by a link 66 (see FIG. 3).

As is conventional, portions of the pneumatic circuit are isolated by check valve, Y-connectors 67. In addition, sensors 68 are provided to disable the cable payout circuits unless there is a desired minimum pressure available in the pneumatic lines. If desired, an additional interlock can disable the control circuits when the engine 12 is not running.

As those skilled in the art can appreciate, the hoist drum control just discussed gives automatic drum braking and yet provides smooth transition, without shock loading, between the drum being locked and driven. Control of the selected drum is through a single lever so as to greatly simplify drum operation, and automatic clutching permits a plurality of drums to be driven from a single power source.

I claim as my invention:

1. A control for a drum holding cable intended for tension loading comprising, in combination, a source of driving torque, a converter interposed between said source and said drum, said converter having a sleeve interposed between driving elements which is movable from a first blocking position in which no torque is transmitted to said drum through a range of positions in which smoothly increasing amounts of torque are transmitted to the drum, a brake for said drum which is self-energizing in the direction of drum rotation that pays cable out and which is capable of slipping in the opposite direction of drum rotation, means for normally holding said brake engaged, a first actuator for opposing said means and releasing said brake, means for normally holding said sleeve in said first position, a second actuator for opposing said last named means and moving said sleeve from said first position through said range of positions, a control device which is manually moved for applying proportional forces through said first and second actuators, a rotation sensor coupled to said drum for detecting more than slight rotation of the drum in the direction to take up cable, and means interposed between said control device and said first actuator for blocking said force application by the first actuator, said last named means being controlled by said sensor so that the blocking effect is eliminated when said slight rotation is detected, whereby said clutch is not engaged.

3. The combination of claim 1 including a hydraulic motor for driving said drum in a direction to pay off cable from the drum, means associated with said control device for simultaneously actuating said motor and said first actuator, said motor being associated with a pressure relief valve so that, if said motor is opposed by torque through said converter, hydraulic fluid will bypass the motor. 

1. A control for a drum holding cable intended for tension loading comprising, in combination, a source of driving torque, a converter interposed between said source and said drum, said converter having a sleeve interposed between driving elements which is movable from a first blocking position in which no torque is transmitted to said drum through a range of positions in which smoothly increasing amounts of torque are transmitted to the drum, a brake for said drum which is self-energizing in the direction of drum rotation that pays cable out and which is capable of slipping in the opposite direction of drum rotation, means for normally holding said brake engaged, a first actuator for opposing said means and releasing said brake, means for normally holding said sleeve in said first position, a second actuator for opposing said last named means and moving said sleeve from said first position through said range of positions, a control device which is manually moved for applying proportional forces through said first and second actuators, a rotation sensor coupled to said drum for detecting more than slight rotation of the drum in the direction to take up cable, and means interposed between said control device and said first actuator for blocking said force application by the first actuator, said last named means being controlled by said sensor so that the blocking effect is eliminated when said slight rotation is detected, whereby said manual control device can smoothly apply torque to said drum and, when the drum begins to take up cable, the brake is released with there being proportional forces controlling both the application of torque and operation of the brake.
 2. The combination of claim 1 including a clutch interposed between said converter and said drum, means for engaging said clutch only upon initial movement of said control device so that said source of torque and said converter can be used for powering additional drums under the control of other devices when said clutch is not engaged.
 3. The combination of claim 1 including a hydraulic motor for driving said drum in a direction to pay off cable from the drum, means associated with said control device for simultaneously actuating said motor and said first actuator, said motor being associated with a pressure relief valve so that, if said motor is opposed by torque through said converter, hydraulic fluid will bypass the motor. 